Electrical stimulation of biological tissue is currently used or under active consideration for use in the treatment of a variety of clinical problems. While the possibility of selective electrical stimulation of a localized region within the body by completely non-invasive means has been postulated on theoretical grounds, such stimulation has yet to be demonstrated experimentally. However, the selective stimulation of localized region within the body can be achieved by implanting a very small diode at the desired site and then applying a pulsed radio frequency field by means of electrodes or a coil on or near the surface of the body. Our work is focused at obtaining a reasonably completed theoretical description of the several possible systems. For the system involving electrodes on the surface of the body, this involves working with a model in which circular electrodes are placed on the surface of a seim-infinite homogeneous medium and then relating the direct current component of diode current to the geometry of the diode implant, the geometry of the electrodes, and to the radio frequency power level. For the system involving a coil, this involves working with a semi-infinite medium and relating the direct current component of diode current to the relevant geometrical factors and to the power input to the coil.